Air dryer equipment

ABSTRACT

An air dryer for automatically drying mass production items after their being processed through wash and rinse sections. The dryer includes an air knife capable of directing a concentrated uniform blast of air at the production items being dried as they pass through the air knife section of a conveyor line.

United States Patent [191 DeVerter et a1. 1

[ AIR DRYER EQUIPMENT [75] Inventors: Walton DeVerter, Chicago; John M.Lamberty, Des Plaines, both of 111.

[73] Assignee: Dee Electric Company, Chicago, 111.

[22] Filed: Dec. 20, 1972 [21] Appl. No.: 316,884

[52] U.S. Cl. 15/302, 15/306 B, 15/316 R, 134/72 [51] Int. Cl. A471 5/38[58'] Field of Search.. 15/302, 306 R, 306 A,306 B, 15/345, 346, 316 R;134/72 [56] References Cited UNITED STATES PATENTS 862,695 8/1907Baldwin 15/345 1,771,558 7/1930 De Repentigny 15/306 A 3/1950 Dunakin etal. 15/345 X 5] Nov. 26, 1974 2,713,011 7/1955 Durst 15/316 X 2,818,5951/1958 Rosewall 15/306 A 3,498,303 3/1970 Eaves et al 15/302 X 3,525,1167/1970 Shaffer v 15/306 A 3,570,505 3/1971 Randall 134/72 8/1973 Arnett15/306 A Primary ExaminerRobert L. Bleutge Assistant Examiner-C. K.Moore Attorney, Agent, or Firm-Alter Weiss Whitesel & Laff [57] ABSTRACTAn air dryer for automatically drying mass production items after theirbeing processed through wash and rinse sections. The dryer includes anair knife capable of directing a concentrated uniform blast of air atthe production items being dried as they pass through the air knifesection of a conveyor line.

7 Claims, 6 Drawing Figures PATENTEL f lm! 2 6 I974 sum 3 or 3 FIG.5

AIR DRYER EQUIPMENT This invention relates to the automatic dryingequipment for drying production items as they pass on a conveyor linethrough different, processing stations, and is more particularlyconcerned with the air knife section of power wash cleaning systems,such as are used in fabricating printed circuit boards, or the like.

During the power wash cleaning operation, the production item beingtransported by a conveyor passes through a plurality of wash and rinsesections. The wash and rinse operations are accomplished usingappropriate chemicals.

It is necessary in the production of equipment with high reliability tothoroughly dry such equipment. The drying equipment forces drafts of hotair against the conveyor transported items. However, there is a limit onthe time and temperature of the hot air being directed against theprinted circuit boards. If these limits are exceeded, then theres dangerof damaging the components of the printed circuit boards. Further, anychemical residue remaining on the boardcould adversely effect thecomponents.

Therefore, to expedite the drying processes, air knives are used at theonset of the drying process. More particularly, the air knife directsfiltered stream of air against the production items to be dried such asprinted circuit boards. The stream. of air, if properly directed,removes most of the superfluous liquids adhering to the boards after thewash and rinse processes to thereby minimize residue and thereby enablethe convection drying process to be accomplished with less caloricinput.

A major problem in the past has been to j provide a uniform stream ofair across the entire printed circuit board as it passes through the airknife. In the past the air knife has terminated at a cylindrical chamberhaving apertures therein through which a stream of air passes onto theprinted circuit board passing juxtaposed thereto. To obtain the desiredresult, it is necessary that the air-enter the terminating chamber a arelatively high pressure. Due to the high pressures, it has beenvirtually impossible to obtain a uniform stream of air from thecylindrical chamber.

One end of the air knife terminating chamber is closed; The other end isconnected to duct work bringing the air from the air prime mover, suchas a centrifugal pump or the like. The air, upon striking the closed endof the chamber is forced back into the chamber and sets up pressurepeaks and valleys in the chamber as the returning air intenningles withthe forward moving stream of air. Thus, at some apertures there ispractically no air pressure at all, and consequently, no air flow; whileat other apertures there is high pressure and a large amount of airflow. The large amount of air flow at these apertures set up turbulenceswhich further disturb the flow of air and create unsymmetrical pressureand flow patterns. Attempts have been made to provide uniform air flowby varying the size of the apertures. Such attempts have not provedsuccessful.

In practice, portions of the printed circuit board passing juxtaposed tothe air knife chambers are not subjected to the concentrated flow of airfrom the air knife. Thus, portions of the printed circuit boards remainladen with droplets of liquid as the printed circuit boards pass intothe hot air convection dryer. Therefore, the drying operations ofpresent day equipment are faulty and in need of improvement.

Accordingly, an object of the present invention is to provide new andunique power wash cleaning systems wherein the products being processedare thoroughly dried and wherein practically no residual trace of thecleaning chemical remain on the products.

A related object of this invention is to provide power wash cleaningsystems wherein thorough drying occurs without subjecting the productsbeing processed to danger from hot air dryers operating at a temperatureor for a time duration that may be injurious to the items being dried.

A'related object of this invention is to provide a new and unique airknife.

Still another object of this invention is to provide air knivesproviding uniform air flow over the entire surface of the products beingprocessed.

Yet another object of this invention is to provide air knives having airknife chambers which are not cylindrically shaped.

Yet another object of this invention is to provide air knives having airknife chambers that have polygonal cross sections.

Still another object of this invention is to provide air knives whereinthe air knife chambers are rectangular .parallelepipeds having aperturesalong one of the iongitudinal vertices of the rectangle.

Yet another object of this invention is to provide air knives havingterminating chambers that, are wedge shaped with apertures at theangular meeting point of the biased planes. The apex of the angle is thepart of the chambers closest to piece parts being processed.

A preferred embodiment of the power wash cleaning system comprises aplurality of wash and rinse stations followed by an air knife station.The air knife station leads into a hot air dryer station. The air knifestation comprises an air prime mover pump that includes a fan and scrollof arcuate compartment leading into ducts. The ducts terminate in a pairof spaced apart, oppositely disposed air knife chambers. The chambersare wedge shaped in part with a series of apertures along the apecies ofthe wedges.

As the products pass through the space between the chambers on a mesh orscreen, they are subjected to a continuous, uniform, strong stream ofair against both sides of the products which removes droplets of thewash and rinse fluid from the product passing therethrough.

The airflow is extremely uniform and because of the shape of thechambers, they can be positioned a minimum distance from the printedcircuit boards or the like. The proximity of the product being processedand the lack of turbulence in the chambers maximizes the drying effectof the drying station while minimizing the exposure of the components ofthe printed circuit boards to the deleterious effects of heat andresidue.

The above enumerated and other features and objects of this inventionwill now be explained in detail with the aid of the accompanyingdrawings, wherein:

FIG. 1 is a plan view of a typical power wash cleaning system utilizedin processing printed circuit boards after they are automaticallysoldered;

FIG. 2 is a pictorial view of the air knife and hot air dryer stationsof the power wash cleaning system of FIG. 1;

partment;

FIG. 5 is a plan view of the bottom one of a pair of horizontallymounted air knife chambers showing the apertures as they appear to theproducts passing thereover; and

FIG. 6 shows two alternative shapes for the air knife chambers.

In the power wash cleaning system 11 of FIG. 1, a pair of wash stations12 and 13 are shown. The wash stations are followed by a rinse stationgenerally indicated at 14. The drying station comprises the air knifesection generally indicated as 16, followed by the hot air dryer sectiongenerally indicated as 17. The goods are either hand carried and loadedonto the power wash and cleaning system of FIG. 1, or brought there by acontinuous conveyor belt from another processing station such as anautomatic fluxer and soldering station.

In the plan view of FIG. 1 there is shown an initial exhaust air duct 18in a hood 19. The exhaust duct aids in removing the vapors resultingfrom the soldering process. There is, of course, sufficient room betweenthe hood 19 and the meshed carrier or conveyor belt 21 for passage ofthe printed circuit boards.

Each of the wash and rinse stations may be separately controlled bycontrols such as the control boxes 22, 23 and 24 associated with thewash and rinse stations 12, 13 and 14, respectively. Similarly the airknife and dryer stations 16 and 17, respectively are controlled usingcontroller 26.

Wash sections and rinse sections generally comprise horizontallydisposed spaced apart apertured pipes for directing streams of fluids atthe products being processed sas they pass therebetween. The conveyorsare usually of the continuous type and are seen at the ends of the powerwash cleaning system 21 and 27. Generally speaking, the fluids, exceptfor the rinse section wherein in a typical situation clean hot water isused, are recirculated. The plumbing for recirculating the washing fluidis schematically shown at 28 and 29. The hot water input and drain areschematically indicated at 31. Certain pertinent portions of the airknife are indicated at 16. For example, the fan and scroll compartmentof the air prime mover are generally indicated as 32. The intake isfiltered and the filter is schematically indicated at 33.'The ductscoupling the scroll to the chamber duct work are schematically shown as34.

Certain pertinent portions of the hot air dryer are indicated at 17. Forexample, the power input to the hot air dryer is indicated at 36. Theducts indicated at 37 are for directing the hot air through a dryer hood38.

A portion of the meshed carrier 41 carrying printed circuit boards suchas boards 42 and 43 through the power wash cleaning system isgraphically depicted in FIG. 1.

FIG. 2 pictorially shows the air knife 16 and dryer station 17 ofFIG. 1. As can be seen, both stations include a section of the base tank44 which contains the endless conveyor system. Component parts of theair knife station are the previously mentioned filter 33 at the intaketo the fan and scroll compartment 32. The scroll compartment comprises,for example, an intermediate compartment effectively directing the airfrom the air prime mover, such as a fan. into the ducts. Only a portionof the scroll is shown, since scrolled compartments are well known tothose skilled in the art. The pump and scroll compartments are locatedbetween plates 46 and 47. The filter 33 is shown as a double filtercomprising sections a and b. The filter is held onto plate 46 by meanssuch as threaded fastener 48 passing through circular plate 49 to retainfilters 33a and 33b juxtaposed and abutting the entrance of the airintake entrance (not shown) to the pump and scroll 32. The plates 46 and47 are held together with threaded fasteners such as threaded fastener51 passing through both plates. A bushing 52 between the platesmaintains a set distance between the plates sufficient for the passageof duct 53 located at the end of the scroll.

Duct 53 terminates at flange 54a. A first and a second knife chamber 57,58, spaced apart and horizontally disposed traversing the conveyor'orcarrier are provided. The first air knife chamber 57 is shown positionedabove the carrier and is attached to flange 54b. The second air knifechamber is attached to the flange 54b through duct 61.

The chambers themselves are generally shown as rectangularparallelepipeds having apertures at the vertex of one of thelongitudinal angles such as apertures 62 in the chamber 58 and apertures63 in the compartment 57. The chambers are positioned so that theapertures are as close as possible to' the printed circuit boardspassing therebetween.

Air is forced through the filter 33 A and B at the intake of the primemover and through the fan and the associated scroll through duct 53attached to air knife chamber ducts 61 and to 59, through the chambers58 and 57 and through the apertures at the vertices of the longitudinalangles to strike the bottom and top of the printed circuit boardspassing the spaced apart chambers. It should be understood, of course,that the printed circuit boards could be held vertically rather thanhorizontally, and then the air knives would then be oriented to apply auniform stream of air in the horizontal direction to strike thecomponents and the boards to drive excess moisture therefrom.

The air coming from the apertures is focused by the shape of thechambers 57 and 58 contiguous to the apertures and flows forcefullythrough the apertures. In addition, it has been found that the angularshape proximate to the apertures avoids the turbulence in the air causedby the air bouncing off a closed end of the chamber and interfering withthe incoming air.

The air knife chambers 57 and 58 are joined to the ducts by means suchas male threads 64 and 66 on circumferential portions at the duct endsof the chambers. Matching female threads are located at thecircumferential sections 67 and 68, respectively, of the ducts 59 and61. Naturally, pipe threads are used to prevent air leakage at thecoupling of the ducts and the air knife chambers. Also, the threadsenable orientation of the chambers so that the aperture portions of thechambers are directly opposite each other, directing the air mostefficiently at the circuit boards.

As shown in FIG. 2 the combined air knife and hot air dryer sectionincludes a biased drain sheet 67 to enable excess moisture to flow tothe drain. It is biased to gravitationally force the excess moisture tothe drain. Immediately after the air knife section, a hood 68 isprovided leading from duct work 69 for directing heated air through theduct work and onto the printed circuit board.

Because of the efficiency of the air knives shown and described herein,the drying job is more efficiently executed.

FIGS. 4 and 5 are exemplary showings of the air knife chamber such asair knife chamber 58 having a series of apertures 62 therein at onecorner thereof.

FIG. 6 at A, B and C show different embodiments of the cross-sections ofdifferent embodiments of the air knife chambers 58. The cross-section ofair knife chamber of FIG. 6 A, for example, has two sections 71 and 72which are at an angle to each other but are separated by an aperturesuch as aperture 73. The bottom of the chamber 74, however, is flat sothat the configuration of the air knife chamber of FIG. 6A is triangularor wedge shaped with a polygonal cross section.

FIG. 6 B shows the cross-section of the shape of the chamber 58 shown inFIGS. 4 and 5.

FIG. 6 C shows the angular sections 71, 72 separated by the aperture 73and wherein the bottom of the chamber is also angularly disposed andcomprised of sections 76 and 77 joined together at angle 78. FIG. 6 l

C is very similar to FIG. 6 B except for the difference in the angles.

In operation, then, articles of manufacture, such as printed circuitboards are transfered from the automatic soldering operation to thepower wash cleaning system where it first passes underneath an exhaustduct on a conveyor whose beginning is shown at 21. The printed circuitboard then passes through a sprinkler washsection comprised of aplurality of overhead and bottom sprinklers that thoroughly sprinkle awashing solution onto the boards.

The rinse section generally uses hot water which is also sprinkled fromthe top and the bottom with a multiple sprinkler arrangement. After therinse section, the article of manufacture passes through air knifechambers. The present system using the air knife having a parallelepipedchamber provides a uniform stream of air to drive excess moisture andfluid from the article of manufacture prior to-the hot air dryerstation.

While the principals of the invention were described above inconnectionwith the specific apparatus and application, it is to beunderstood that this description is made only by way of example and notas a'limitation on the scope of the invention.

gular corners of said parallelepiped shaped chamber, and I means forsupplying air under pressure to said chamber at an angle to saidapertures so that said air is said chamber having a series of aperturesfor direct- .ing the air uniformly against the articles of manufacturepassing proximate thereto,

means for supplying air under pressure into said chamber, and

said apertures being at one of the longitudinal meeting points of twosides of the said chamber.

3. The power wash cleaning system of claim 2 wherein the means forsupplying air to the chamber includes coupling means for joining themeans for supplying air to the chamber,

said coupling means comprising an air entry opening at one end of saidchamber,

said opening surrounded by a pipe threaded section,

said means for supplying air under pressure comprising pump means,

air filter means at the input to said pump means,

said pump means discharging into a scroll compartment,

said scroll compartment discharging into duct means,

and

the end of said duct means being aligned with the longitudinal axis ofsaid chamber and having mating pipe threads for receiving said pipethreaded section of said chamber.

4. The power wash cleaning system of claim 2 wherein said chamber is aparallelepiped comprising side walls and a pair of end walls, v

an opening at one of said end walls for coupling said chamber to saidmeans for supplying air,

said air chamber being closed at the other of said end walls, and

said apertures being along the junction of a pair of said side walls ofsaid chamber. 5. The power wash cleaning system of claim 2 wherein saidapertures are of varied sizes.

6. The power wash cleaning system of claim 2 wherein said apertures areof the same size;

7. The power wash cleaning system of claim 2 wherein said apertures arethe same'size and are evenly spaced.

1. An air knife for use in directing a uniform stream of air against anarticle to be dried, said air knife comprising a rectangularparallelepiped shaped chamber, a series of apertures along one of thelongitudinal angular corners of said parallelepiped shaped chamber, andmeans for supplying air under pressure to said chamber at an angle tosaid apertures so that said air is uniformly dispersed through saidapertures at products to be dried passing proximate to saidapertures.
 1. An air knife for use in directing a uniform stream of airagainst an article to be dried, said air knife comprising a rectangularparallelepiped shaped chamber, a series of apertures along one of thelongitudinal angular corners of said parallelepiped shaped chamber, andmeans for supplying air under pressure to said chamber at an angle tosaid apertures so that said air is uniformly dispersed through saidapertures at products to be dried passing proximate to said apertures.3. The power wash cleaning system of claim 2 wherein the means forsupplying air to the chamber includes coupling means for joining themeans for supplying air to the chamber, said coupling means comprisingan air entry opening at one end of said chamber, said opening surroundedby a pipe threaded section, said means for supplying air under pressurecomprising pump means, air filter means at the input to said pump means,said pump means discharging into a scroll compartment, said scrollcompartment discharging into duct means, and the end of said duct meansbeing aligned with the longitudinal axis of said chamber and havingmating pipe threads for receiving said pipe threaded section of saidchamber.
 5. The power wash cleaning system of claim 2 wherein saidapertures are of varied sizes.
 6. The power wash cleaning system ofclaim 2 wherein said apertures are of the same size.
 7. The power washcleaning system of claim 2 wherein said apertures are the same size andare evenly spaced.